might i say, all you have to do is memorize a pattern for games like ddr and just keep practicing that.
league is different every time.
Apply the "mines" mod, which replaces random notes with mines, which if hit, reduce your life. That, and a mod that basically does random unpredictable stuff to the playfield. There are also mods to "scramble" steps.
Even then, predictability isn't something that would make DDR easy, or any game for that matter. No matter how many times you practice, a level 17 song with 12 notes a second is going to drain your stamina instantly every time.
Side note: most people play songs about five times and can pretty much max out their skill on that one song, because nobody memorizes patterns. The only case in which memorization is required, is if there are speed changes in the song which cannot be read normally. Half of the skill is purely in reading the notes. A lot of my friends always ask me "do you memorize all that??" Bitch, you think I feel like memorizing five minutes worth of patterns?